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Several cosmological phenomena generate a stochastic gravitational wave background (GWB). One of the fundamental mechanisms is the generation of GWB from the primordial fluctuations in the early universe. This simple and rudimentary phenomenon encodes into GWB, the information about the initial conditions of cosmological perturbations that evolve into the structure of current universe. Given the signal of stochastic GWB observed by the International Pulsar Timing Array collaboration and the forecasts of upcoming observatories such as Einstein Telescope, it becomes imperative to carefully analyse the primordial mechanisms generating GWB and compute predictions such as its spectral shape, polarizations and anisotropies. In this talk, I shall demonstrate how such analyses of GWB can address open issues in cosmology such as primordial non-Gaussianity, generation of cosmic magnetic fields and validity of fundamental symmetries such as parity. I shall also present how GWB forecasts can complement the existing datasets of cosmic microwave background and large scale structure in levying precise constraints on cosmological parameters. I shall conclude with a summary of my recent results and outlook of ongoing projects in this regard. |